1. Field of the Invention
The present invention relates to the fabrication of chrome-plated automotive vehicle wheels, particularly wheels formed of aluminum.
2. Description of the Prior Art
For quite a number of years automotive vehicle wheels have been plated with chrome to enhance their corrosion resistence, as well as to improve their aesthetic appearance. Chrome-plate aluminum wheels and also chrome-plated steel wheels are in widespread use on automotive vehicles.
In the fabrication of an automotive vehicle wheel, particularly an aluminum wheel, the wheel is often constructed of two basic parts. That is, the wheel includes an outer, annular metal wheel rim and an inner wheel center, which is sometimes termed an xe2x80x9cinnerxe2x80x9d0 or xe2x80x9cfillerxe2x80x9d0 in the automotive vehicle wheel fabrication industry.
In the construction of such an automotive vehicle wheel, the outer, annular metal wheel rim and the inner metal wheel center are first fabricated separately. The outer metal wheel rim is formed with a radially inwardly facing center-receiving surface while the wheel center is formed with an outwardly facing rim-contact surface. The diameter of the inwardly facing center-receiving surface of the rim and the rim-contact surface of the wheel center are nominally coextensive with each other.
In order to allow the wheel center to be set within the wheel rim, the annular metal rim is heated, typically to a temperature of between about 375xc2x0 F. and 450xc2x0 F. The coefficient of thermal expansion of the metal of which the rim is formed causes the opening in the wheel rim defined by the center-receiving surface to increase sufficiently so that the wheel center can be set within the wheel rim in longitudinal and coaxial alignment therewith. When the wheel rim is allowed to cool, it contracts, thus causing its center-receiving surface to shrink radially inwardly upon the rim-contact surface of the wheel center so that these surfaces reside in tight, intimate contact with each other.
After the wheel rim and center have been assembled together in this fashion, they are welded together. More specifically, an annular weld is created about the inboard circumference of the inboard extremities of the center-receiving surface of the metal wheel rim and the rim-contact surface of the wheel center. The term inboard, as utilized herein, refers to the side of the wheel that faces the brake mechanism, while the term outboard refers to the side of the wheel facing outwardly away from the brake mechanism and away from the structure of the vehicle and against which the lug nuts are fastened when the wheel is in use.
Following the welding process many wheels are chrome-plated to provide corrosion protection and to enhance their appearance. To chrome plate a wheel, the wheel body, that is the assembled wheel rim and wheel center welded together, must first be treated to ensure that the chrome-plating will adhere to the aluminum or other metal of which the wheel body is formed. In a typical chrome-plating process the exposed surfaces of the metal wheel rim and metal center forming the wheel body are first cleaned to remove any grease or other film or contamination on the wheel. The wheel is then chemically stripped. That is, it is placed in an acid or caustic bath to further remove contaminants and condition its surface to accept the chrome-plating. The exposed surfaces of the wheel are then polished, typically in stages beginning with a grit of perhaps one hundred twenty and proceeding to a finer grit, which may be as fine as an eight hundred, for example.
Following the step of polishing, the wheel is then copper-plated. This step is performed by placing the wheel in an acid solution containing copper. Following the copper plating process, the wheel is then buffed again and plated, first with nickel and then with chrome. Both the nickel and chrome-plating solutions are acid bath solutions. Following the step of chrome plating, the wheel is then ready for use.
Most wheels that are properly treated in the plating process will retain their chrome plating in unblemished condition for many years. However, in a significant number of wheels, the acids and other chemical employed in the plating process seep into the interface between the radially inwardly facing center receiving surface of the wheel rim and the radially outwardly facing rim-contact surface of the wheel center at the unwelded, outboard extremities of these surfaces, despite the extremely tight fit between these surfaces. Some residual quantities of acids and other chemicals from the plating process are then trapped beneath the chrome overcoating layer that is applied to the exposed surfaces of the wheel. These residual acids and caustic chemicals then attack the chrome overcoating from beneath to form blisters in the chrome coating on the wheel. Such blisters are unsightly when they form, and inevitably break, thereby creating gaps in the chrome coating on the wheel. The portion of the wheel body exposed at these gaps is thereby subject to deterioration. The owner of the wheel is then quite dissatisfied, and the wheel is often returned as being defective.
While the great majority of chrome-plated wheels do not suffer this type of degradation, the number of wheels that do prove to be defective in this manner is significant enough to represent a continuing annoying and expensive problem to entities that chrome plate wheels. While this problem has persisted for years, no satisfactory solution has heretofore been found to prevent it.
The present invention involves an automotive vehicle wheel that is fabricated in such a manner as to prevent residual acids and other chemicals from seeping into the interface between the radially inwardly facing center receiving surface of the metal wheel rim and the radially outwardly facing rim-contact surface of the wheel center during the treatment of the wheel in the chrome-plating process. The invention is equally applicable to wheels which may be plated with other metals, such as nickel, for example.
The present invention involves a unique wheel construction that forms a barrier to residual acids and other chemicals at the outboard extremity of the interface between the contacting surfaces of the wheel rim and the wheel center. This barrier prevents damaging chemicals from flowing or seeping into the interface between the wheel rim and the wheel center.
The unique construction of a plated automotive vehicle wheel according to the invention involves the formation of a narrow, annular channel into the radially outwardly facing rim-contact surface of the wheel center near the outboard extremity of that surface, and the provision of a resilient O-ring within that channel. The O-ring is present in the channel when the wheel rim and wheel center are assembled together and is partially compressed to form a fluid-tight seal between the wheel rim and the wheel center as the wheel rim cools following insertion of the center into it. By locating the channel and resilient O-ring quite close to the outboard extremities of the mating surfaces of the wheel rim and the wheel center, damaging chemicals are excluded from entering between the surfaces.
In one broad aspect the present invention may be considered to be a metal-plated automotive vehicle wheel comprising: an outer, annular metal wheel rim having a radially inwardly facing center-receiving surface that has opposing inboard and outboard extremities; a metal wheel center set within the wheel rim and having a radially outwardly facing rim-contact surface that resides in face-to-face contact with the center-receiving surface between the inboard and outboard extremities thereof, and wherein a radially inwardly directed channel is defined in the rim-contact surface proximate the outboard extremity of the center-receiving surface; and a resilient O-ring is disposed in the channel and compressed against the center-receiving surface of the rim, and said wheel center is welded to the wheel rim at the inboard extremity of the center-receiving surface, and the wheel rim with the wheel center set therewithin are externally plated with a metal overcoating.
While the wheel rim and the wheel center may be formed of a wide variety of metals, they are both typically formed of aluminum. Also, the metal overcoating may be a coating of a wide variety of metals, but typically contains chromium.
Because the annular metal wheel rim is heated to expand its inner radius in order to set the wheel center within it, the resilient O-ring should be formed of a material that will withstand an elevated temperature, typically a temperature of at least 400xc2x0 F. without melting. In a preferred embodiment of the invention the resilient O-ring is formed of a silicon-based rubber compound. Suitable materials for fabricating the O-ring are sometimes referred to as xe2x80x9cengineered rubbersxe2x80x9d.
The channel for the O-ring should be located quite close to the outboard extremity of the interface between the mutually contacting surfaces of the wheel rim and the wheel center. Preferably, the channel is located no more than about 0.04 inches from the outboard extremity of the rim-contact surface, and preferably is located about one-thirty-second of an inch from the outboard extremity of the rim-contact surface.
Typically the channel is directed into the structure of the wheel center perpendicular to the axis of the wheel. However, in some wheels the surface configuration of the wheel center is such that it is inadvisable to from the channel for the O-ring in a plane perpendicular to the wheel axis. In some wheel configurations the periphery of the wheel center flares outwardly at its outboard extremity so that there would be insufficient structure remaining beneath the rim-contact surface if the channel is oriented in a plane perpendicular to the axis of the wheel. In such a situation the channel should be defined at an angle relative to the wheel axis inclined radially inwardly and away from the outboard extremity of the wheel contact surface.
The resilient O-ring will still make contact both with the floor of the channel defined in the rim-contact surface of the wheel center and also the radially inwardly facing center-receiving surface of the wheel rim. By defining the channel at an inclination relative to the wheel axis, however, sufficient structure remains at the outboard periphery of the wheel center so that the structural integrity of the wheel center is not compromised.
The channel that is defined in the rim-contact surface of the wheel center is quite narrow and quite shallow. Typically, the channel will be slightly less than about an eighth of an inch in width and an eighth of an inch in depth. The undeformed cross-sectional diameter of the O-ring is then preferably about one-eighth of an inch.
In another broad aspect the invention may be considered to be an improvement in an externally plated metal automotive vehicle wheel formed with an outer, annular metal wheel rim having a radially inwardly facing center-receiving surface that has opposing inboard and outboard extremities and an inner metal wheel center having a radially outwardly facing rim-contact surface that has a inboard and outboard extremities and which resides in contact with the center-receiving surface. As in conventional wheels of this type, the wheel rim and the wheel center are welded together at the inboard extremities of the rim-contact surface and the center-receiving surface. According to the improvement of the invention a radially inwardly directed channel is defined in the rim-contact surface proximate the outboard extremity thereof. Also, a resilient, annular O-ring is disposed in the channel and is compressed against the center-receiving surface of the wheel rim. As previously indicated, the fabrication of a wheel in this manner presents a barrier to acids and other chemicals from entering into the interface between the wheel rim and the wheel center.
In still another broad aspect the invention may be considered to be a method of fabricating an externally plated metal wheel. The method is comprised of several steps. An outer, annular metal wheel rim is formed with external surfaces and a radially inwardly facing center-receiving surface that has opposing inboard and outboard extremities. A metal wheel center is formed with external surfaces and an outwardly facing rim-contact surface having opposing inboard and outboard extremities. A radially inwardly directed annular channel is defined into the rim-contact surface proximate the outboard extremity thereof. A resilient, annular O-ring is inserted into the annular channel. The wheel rim is heated to increase its diameter due to thermal expansion. The wheel center is then set within the heated wheel rim. The wheel rim is cooled, whereby the center receiving surface compresses the resilient o-ring and shrinks into intimate contact with the rim-contact surface, both inboard and outboard from the resilient O-ring between the inboard and outboard extremities of both the rim-contact surface and the center-receiving surface. The wheel center is welded to the wheel rim at the inboard extremities of the rim-contact surface and the center-receiving surface to thereby produce an assembled wheel body. This assembled wheel body is then plated with a metal overcoating.
Typically, the assembled wheel body is treated prior to plating to produce a finish thereon that will accept the metal plating. This treatment normally involves dipping the wheel in several acid baths and/or caustic baths having a high pH and ultimately into a liquid solution containing chromium.
The invention may be described with greater clarity and particularity by reference to the accompanying drawings.